The present invention relates to a method for combining an elastomer thread with an unextendable thread and to an associated machine for implementing the method, in which said elastomer thread is supplied upstream of the group performing false twisting of the two threads. It is known that in the art of producing yarns for weaving there exists the need to elasticize these yarns by combining an elastomer thread with the thread of unextendable fabric.
The known techniques for performing this combining operation basically consist of two types, i.e. so-called:
interlacing: performed by means of air devices which combine the thread and elastomer, both of which have already been pre-stretched/texturized separately. Although sufficiently fast, this method requires two separate apparatus for the separate preliminary processing and the subsequent combination of the unextendable thread and the elastomer thread, with the consequent need for intermediate spooling and transfer of the spools from one machine to the other, resulting in long cycle idle times. In addition to this, the method of air interlacing is unable to guarantee a high quality of finish of the final yarn (so-called velvet touch) which is wound onto the spool to be transferred for subsequent processing;
overlaying: based on a machine which unwinds an unextendable thread from a special reel which has been prepared beforehand and at the same time winds it spirally onto an elastomer yarn. Although this method is able to achieve a much higher quality of the final yarn, it is, however, slow and requires an intermediate step for preparation of the special reels which are obtained by winding the unextendable thread removed from a spool of already pre-stretched/texturized thread onto another machine, with a consequent increase in the time and costs for production of the elasticized yarn. The technical problem which is posed, therefore, is that of providing an elasticized yarn obtained from the combination of a thread of unextendable fabric with an elastomer thread, by means of a method and an associated machine which are able to operate at much higher speeds and obtain at the same time a high final quality of the elasticized yarn.
Within the scope of this problem a further requirement is that the method should be able to be implemented by means of a single simplified and compact machine which reduces to a minimum the intermediate steps of preliminary processing of the yarn and the elastomer and the need to have intermediate spools and/or reels. These technical problems are solved according to the present invention by a method for combining an elastomer thread with an unextendable thread and an associated machine for implementing the method, in which said unextendable thread is supplied upstream of the group for false twisting the two threads.